Visual acuity, fatigue play role in exam interpretation

February 11, 2006

Sharper eyesight may not guarantee a better read, according to research presented at the 2005 RSNA meeting. Fatigue does play a large part in interpretation accuracy, however, and nearly 50% of participants in a multicenter survey admitted to falling asleep while reading a study on call.

Sharper eyesight may not guarantee a better read, according to research presented at the 2005 RSNA meeting. Fatigue does play a large part in interpretation accuracy, however, and nearly 50% of participants in a multicenter survey admitted to falling asleep while reading a study on call.

Respondents attributed more than 17% of missed findings to lack of sleep, said Dr. Nabile Safdar, an assistant professor of diagnostic radiology at the University of Maryland Medical Center in Baltimore.

Few studies have been published in the medical literature regarding visual acuity in radiologists. One study published in a 1997 issue of European Radiology found that of 25 radiologists tested in the U.K., five had suboptimal visual acuity and could benefit from further eye correction (Eur Radiol 1997;7(1):41:3).

"There have not been a lot of studies on this topic until now, and more work needs to be done," Safdar said. "I think part of the reason may be that people may have been afraid to find out what the answer to these studies would be. They are potentially very self-critical."

Safdar and colleagues originally set out to measure the visual acuity of radiologists in a soft-copy environment and to determine whether that acuity decreased over a workday.

Researchers measured visual acuity in 23 radiologists at three large tertiary-care hospitals. Participating radiologists used both 5-megapixel CRT displays and 2-megapixel LCDs. Investigators administered vision tests between 7:50 a.m. and 10:30 a.m., noon and 3:30 p.m., and after 3:30 p.m.

The radiologists also answered questions about their age, history of ophthalmic surgery, and medical history, as well how many hours of sleep they had received the previous night.

Safdar reported that the average visual acuity of all the radiologists was 20/16, better than a normal 20/20 score. He found no significant difference in visual acuity as measured during different times of the day.

"We were, however, surprised that over one-fifth of the radiologists had less than 20/20 vision," Safdar said.

Some radiologists even had 20/30 vision, which would be the equivalent of sitting about 50% farther away from their workstations than they normally do while trying to interpret an exam, he said.

On average, radiologists had not had an eye exam in more than two years, according to study results.

"It is important for departments to encourage radiologists to maintain their visual health," Safdar said.

But visual acuity is only part of the radiologist performance equation, said Dr. Gary J. Wendt, vice chair of informatics at the University of Wisconsin in Madison, who comoderated the RSNA session.

"Visual acuity is only important if it is bad and goes uncorrected. Education is more important. You can only see what you know," Wendt said.

Another important question is what "resolution" a radiologist's eyes can interpret, he said.

"To take it to an extreme, you could have a 1-inch 9-megapixel monitor, but it is useless unless you view it under a microscope. I think that monitors over 2 megapixels are of little use, but this hasn't been proven. This information would be very useful, as this is the level of consumer-grade monitors," Wendt said.

Fatigue is another important factor in radiologist performance. While most of the radiologists reported nearly seven hours of sleep the night before, those younger than 35 received only an hour of shut-eye or less. Safdar attributed this lack of sleep to the fact that this population of radiologists is most likely to be on call. This finding prompted researchers to conduct a second survey gauging fatigue in the younger population.

Twenty-one respondents replied to the fatigue survey. The average age of the participants was 29. Nearly 30% of the respondents reported that they had fallen asleep while driving when they were on call. More than 47% of the respondents admitted to "microsleeps" while reading a study on call. Safdar defined "microsleep" as a brief period of sleep when the person isn't even aware of dozing off.

The researchers are beginning preliminary studies to further study the effects of fatigue on a radiologist's interpretation accuracy, he said.